Influenza Surveillance Report for MMWR Week 45

The influenza (flu) activity level for Texas for the week ending November 14, 2009 was “regional.” For definitions of flu activity levels please see http://www.cdc.gov/flu/weekly/fluactivity.htm. During week 45, 106 (9.8%) specimens tested by NREVSS laboratories in Texas were positive for influenza. The percentage of visits for influenza-like illness as reported by ILINet providers in Texas was above the regional baseline during week 45.

Reports from Health Service Regions

Reports were received from all Health Service Regions (HSRs) for week 45. All HSRs reported a decreased level of flu activity compared to week 44. For a map of Health Service Regions please visit the following website: www.dshs.state.tx.us/regions/state.shtm

Laboratory Results

During week 45, eight hospital laboratories and public health agencies across Texas reported conducting a total of 1,085 influenza tests (antigen, culture, and PCR) to the National Respiratory and Enteric Virus Surveillance System (NREVSS) sponsored by the Centers for Disease Control and Prevention (CDC). The majority (54%) of influenza tests reported to NREVSS were antigen detection tests; these tests cannot identify the subtype of influenza detected. The results from Texas participants in NREVSS are summarized in the table below.

Testing Information

Week 45

No. of specimens tested

1,085

No. of positive specimens (%)

106 (9.8%)

Positive specimens by type/subtype

Influenza A

104 (98.1%)

Subtyping performed

44 (42.3%)

A (novel H1N1)

44 (100%)

A (H3)

0 (0%)

A (Seasonal H1)

0 (0%)

Subtyping not performed

60 (57.7%)

Influenza B

2 (1.9%)

Additional influenza test results (rapid tests, culture, PCR) were reported from providers and public health departments throughout the state (see county map below).

Novel Influenza A Virus Infections

Please see the Texas Department of State Health Services (DSHS) novel influenza website (http://www.texasflu.org) and the CDC website (http://www.cdc.gov/h1n1flu/) for more information. Data collection for confirmed novel influenza A (H1N1) hospitalizations, intensive care unit (ICU) admissions, and deaths began in Texas on September 20, 2009. Forty-six confirmed novel influenza A (H1N1) deaths were reported in Texas residents and one child from Mexico who died in HSR 6/5S prior to September 20, 2009 (these deaths are included in the cumulative data table below). The table below summarizes the current data by Health Service Region. For more data, please see www.dshs.state.tx.us/txflu/splash/news_media.html.

Cumulative Surveillance Case Summary for Novel Influenza A (H1N1) by Health Service Region and County as of 11/14/2009

Health Service Region

Hospitalizations*

Intensive Care Unit (ICU) Admissions*

Deaths**

Region 1 Total

33

14

4=5

Region 2/3 Total

359

55

30

Region 4/5N Total

52

15

10

Region 6/5S Total

267

113

34

Region 7 Total

85

26

17

Region 8 Total

153

24

18

Region 9/10 Total

356

44

13

Region 11 Total

263

81

37

Texas Total

1,568

372

164

*Reporting for hospitalizations and ICU admissions began on 9/20/2009. ICU admissions are included in the hospitalization totals. **Reporting for deaths began 4/15/2009 and includes a child from Mexico.

Antigenic Characterization

Since June 9, 2009, CDC has reported antigenic characterization results from 25 novel influenza A (H1N1) viruses and 1 seasonal influenza A (H1N1) virus received from the Texas Department of State Health Services (DSHS) Laboratory since April 26, 2009.

Novel Influenza A (H1N1) [25]

All 25 viruses were characterized as A/California/07/2009-like (H1N1), the reference virus selected by the World Health Organization (WHO) as the vaccine strain for the novel influenza A (H1N1) vaccine.

Influenza A (H3N2) [0]

No influenza A (H3N2) viruses from Texas have been characterized since April 15, 2009.

Influenza A (H1N1) seasonal [1]

One seasonal influenza A (H1N1) virus from Texas has been characterized as A/Brisbane/59/2007-like (H1N1), the influenza A/H1 component of the 2009-2010 seasonal influenza vaccine for the Northern Hemisphere.

Influenza B (B/Victoria/02/87 and B/Yamagata/16/88 lineages) [0]

Victoria lineage [0]

No influenza B viruses from Texas have been characterized since April 15, 2009. Yamagata lineage [0]

No influenza B viruses from Texas have been characterized since April 15, 2009.

The national antigenic characterization and antiviral resistance testing results may be found in the CDC weekly flu report at www.cdc.gov/flu/weekly/. The DSHS Laboratory sends a representative sample of influenza viruses to the CDC throughout the flu season.

Antiviral Resistance

Since June 9, 2009, CDC has reported antiviral resistance testing results on 110 novel influenza A (H1N1) isolates received from multiple Texas laboratories since April 26, 2009.

Influenza–Associated Pediatric Mortality

School Closures and Institutional Outbreaks

No school closures or institutional outbreaks were reported during week 45. DSHS has issued guidance for cases of ILI and novel influenza A (H1N1) in summer camps, schools, and congregate facilities. Please see www.texasflu.org for more information. For information on school closures, please see the Texas Education Agency's website at http://www.tea.state.tx.us/index4.aspx?id=5402.

U.S. Outpatient Influenza-like Illness Surveillance Network

Eighty-two providers in Texas reported data to the U.S. Outpatient Influenza-like Illness Surveillance Network (ILINet) (formerly known as the U.S. Influenza Sentinel Provider Surveillance System) on patients with influenza-like illness (ILI) and total patients seen for any reason during week 45. Of the 81 providers who saw patients, 67 (83%) saw at least one patient with ILI. Of all patient visits during this week, 6.55% were due to ILI. The ILI baseline for HHS Region 6 (Arkansas, Louisiana, New Mexico, Oklahoma, and Texas) of the United States is 4.6% for the 2009-2010 season. The baseline is the mean percentage of patient visits for ILI during non-influenza weeks for the previous three seasons plus two standard deviations.